Current imaging methods - X-ray CT, MRI, and PET - are capable of detecting most brain pathologies. CT scans and MRI are considered standard methods for anatomical brain imaging, while PET and functional MRI can assess metabolic brain activity. Optical spectroscopy (OS), a non-invasive technique for bedside monitoring for cerebral hemodynamics and oxygenation, affords continuous, in vivo, real time measurements of cerebral oxy - (HbO) and deoxy-hemoglobin (Hb) up to several centimeters in depth, and can provide crucial information on cerebral hemodynamics and oxygenation during different acute and chronic brain conditions. Using one light source and one detector, it has been demonstrated in animals and humans that optical spectroscopy is capable of detecting temporal changes in cerebral hemodynamics and oxygenation under various physiological and pathophysiological conditions (Preliminary Results Section). Using several light sources and detectors, it has been demonstrated that near-infrared light can be used to image the spatial variations of absorption and scattering properties of highly scattering brain tissue., enabling therefore both anatomical and functional brain imaging (Preliminary Results Section). New reliable continuous wave and frequency domain optical instruments have been developed paving the way for further development of diffused optical tomography (DOT). It is not likely that optical spectroscopy will achieve the anatomical resolution of CT, MRI and PET, but its non-invasive nature, low cost, portability, and capability to obtain continuous real-time information on cerebral hemodynamics and oxygenation under various physiological and pathophysiological conditions, presents its major advantage over the other techniques. To improve imaging resolution, further development of optical probes and imaging algorithms is needed. The purpose of this study is to develop diffuse optical imaging software that will optimize the resolution of anatomical and functional brain imaging. We hypothesize that our imaging software will enable real- time optical imaging with spatial resolution of 5 mm. To test our hypothesis, we are proposing the following specific aims: 1) to build an imager based on optical spectroscopy and diffuse optical tomography we are proposing the following specific aims: 1) to build an imager based on optical spectroscopy and diffuse optical tomography (years 1 and 2); 2) to develop our Photon Migration Imaging code to compare multiple algorithms (years 1-5); 3) conduct phantom studies to test the imager in-vitro (years 2 and 3); 4) conduct a pilot animal (years 2 and 3); 5) conduct a pilot human (MRI-OS-DOT validation) study test the imager in-vivo and obtain experience needed for future human studies (years 4 and 5). The new era in neurological management would be greatly advanced by the technology proposed in this proposal which will allow continuous real time imaging of cerebral hemodynamics and oxygenation, as ell as the detection and monitoring of different kinds of brain pathology.